(VBA) Have autofill for string with specific list of possibilities

I'm building a Class, and one of the Lets is a string that should only contain one of three options: "Blue","Red","Green"

Entering anything else will cause later functions to not work right. When entering a piece of data for a class that is a Boolean there will be an autofill option that will only show True and False. Is there a way to setup an autofill for when declaring that particular let so that those three options pop up?